25 research outputs found
Planar Cooperative Extremum Seeking with Guaranteed Convergence Using A Three-Robot Formation
In this paper, a combined formation acquisition and cooperative extremum
seeking control scheme is proposed for a team of three robots moving on a
plane. The extremum seeking task is to find the maximizer of an unknown
two-dimensional function on the plane. The function represents the signal
strength field due to a source located at maximizer, and is assumed to be
locally concave around maximizer and monotonically decreasing in distance to
the source location. Taylor expansions of the field function at the location of
a particular lead robot and the maximizer are used together with a gradient
estimator based on signal strength measurements of the robots to design and
analyze the proposed control scheme. The proposed scheme is proven to
exponentially and simultaneously (i) acquire the specified geometric formation
and (ii) drive the lead robot to a specified neighborhood disk around
maximizer, whose radius depends on the specified desired formation size as well
as the norm bounds of the Hessian of the field function. The performance of the
proposed control scheme is evaluated using a set of simulation experiments.Comment: Presented at the 2018 IEEE Conference on Decision and Control (CDC),
Miami Beach, FL, US
Detection of Gaussian signals via hexagonal sensor networks
This paper considers a special case of the problem of identifying a static
scalar signal, depending on the location, using a planar network of sensors in
a distributed fashion. Motivated by the application to monitoring wild-fires
spreading and pollutants dispersion, we assume the signal to be Gaussian in
space. Using a network of sensors positioned to form a regular hexagonal
tessellation, we prove that each node can estimate the parameters of the
Gaussian from local measurements. Moreover, we study the sensitivity of these
estimates to additive errors affecting the measurements. Finally, we show how a
consensus algorithm can be designed to fuse the local estimates into a shared
global estimate, effectively compensating the measurement errors.Comment: 16 pages, 4 figures. Accepted. v1-current: corrected typos, added
clarifications, updated and added references, extended intro and final
remark
Collision avoidance for persistent monitoring in multi-robot systems with intersecting trajectories
Persistent robot tasks such as monitoring and cleaning are concerned with controlling mobile robots to act in a changing environment in a way that guarantees that the uncertainty in the system (due to change and to the actions of the robot) remains bounded for all time. Prior work in persistent robot tasks considered only robot systems with collision-free paths that move following speed controllers. In this paper we describe a solution to multi-robot persistent monitoring, where robots have intersecting trajectories. We develop collision and deadlock avoidance algorithms that are based on stopping policies, and quantify the impact of the stopping times on the overall stability of the speed controllers.United States. Office of Naval Research. Multidisciplinary University Research Initiative (Award N00014-09-1-1051)National Science Foundation (U.S.). Graduate Research Fellowship Program (Award 0645960)Boeing Compan
The Isoline Tracking in Unknown Scalar Fields with Concentration Feedback
The isoline tracking of this work is concerned with the control design for a
sensing vehicle to track a desired isoline of an unknown scalar field. To this
end, we propose a simple PI-like controller for a Dubins vehicle in the
GPS-denied environments. Our key idea lies in the design of a novel sliding
surface based error in the standard PI controller. For the circular field, we
show that the P-like controller can globally regulate the vehicle to the
desired isoline with the steady-state error that can be arbitrarily reduced by
increasing the P gain, and is eliminated by the PI-like controller. For any
smoothing field, the P-like controller is able to achieve the local regulation.
Then, it is extended to the cases of a single-integrator vehicle and a
doubleintegrator vehicle, respectively. Finally, the effectiveness and
advantages of our approaches are validated via simulations on the fixed-wing
UAV and quadrotor simulators
Marine Vehicle Sensor Network Architecture and Protocol Designs for Ocean Observation
The micro-scale and meso-scale ocean dynamic processes which are nonlinear and have large variability, have a significant impact on the fisheries, natural resources, and marine climatology. A rapid, refined and sophisticated observation system is therefore needed in marine scientific research. The maneuverability and controllability of mobile sensor platforms make them a preferred choice to establish ocean observing networks, compared to the static sensor observing platform. In this study, marine vehicles are utilized as the nodes of mobile sensor networks for coverage sampling of a regional ocean area and ocean feature tracking. A synoptic analysis about marine vehicle dynamic control, multi vehicles mission assignment and path planning methods, and ocean feature tracking and observing techniques is given. Combined with the observation plan in the South China Sea, we provide an overview of the mobile sensor networks established with marine vehicles, and the corresponding simulation results
Elastic Formation Control Based on Affine Transformations
International audienceThis paper deals with the control of a fleet of nonlinear systems representing AUVs (autonomous underwater vehicles). The purpose is here to design a control law to stabilize the fleet to time-varying formations which are not only circular. A novel framework is proposed to express a general control law for a large class of formations. This is produced by applying a sequence of affine transformations such as translations, rotations and scalings. The paper also includes a cooperative control to distribute the agents along the formation which takes into account the communication constraints. The system was implemented in computer simulation, accessible through Web